The present invention relates to a machine tool for cutting bars, preferably made of silicon, into preferably very fine portions.
French Pat. No. 2,066,707 discloses a machine tool for cutting bars into portions, comprising a frame provided with an upper plate, a support column in the frame, a mandrel mounted to rotate in the support column, an annular saw blade of which the cutting part is made on its inner periphery and which is supported by the mandrel, a motor for rotating the mandrel and the saw blade, a bar-holder carriage arranged to pivot above the upper plate of the frame and about a spindle fixed to the frame and parallel to the axis of rotation of the mandrel and of the saw, and means on the bar-holder carriage for receiving a bar, for placing it into position of cut along the axis of the saw blade after having pivoted the bar-holder carriage and for lowering it step by step beyond the plane of cut of the saw blade.
In the machine tool of French Pat. No. 2,066,707, the mandrel supporting the cutting blade is mounted to rotate in the support column via a compressed air bearing. Although such an arrangement is advantageous for large diameter mandrels driven at a high speed, due to the small axial and radial clearance which may thus be preserved, such a machine tool is nevertheless not adapted to cutting bars, for example silicon bars, of large diameter and of heavy weight, which are more and more frequent at the present time, in view of the progress made in the processes for obtaining monocrystals.